A housing structure of an acoustic controller having a lower case which is lightweight, high in the degree of freedom in shape design, and capable of suppressing a deformation of side walls thereof after being molded. The lower case is integrally formed from resin into a rectangular dish shape having front, rear, left, right, and bottom plates. An upper unit is attached to an open upper part of the lower case. The left and right plates of the lower case have upper parts thereof formed into brim portions protruding outward in the left-to-right direction. Front and rear parts of each brim portion are further protruded outward and formed into flanges that function as mounting portions used for mounting the acoustic controller to a rack.